MINISTRY OF EDUCATION AND TRAINING THE UNIVERSITY OF NHA TRANG LE THI TUONG STUDY ON PRE-PROCESSING AND PRESERVATION OF POST-HARVESTED SEA GRAPES (CAULERPA LENTILLIFERA J AGARDH 1837) SUMMARY OF THE DOCTORAL THESIS Major : Aquatic Product Processing Technology Code : 9540105 KHÁNH HÒA - 2019 The work has been completed at Nha Trang University Science instructor: Vu Ngoc Boi, Associate Professor Nguyen Huu Dai, Associate Professor Reviewer 1: Ngo Đang Nghia, Associate Professor Reviewer 2: Nguyen Duy Nhut, Dr Reviewer 3: Nguyen Duy Thinh, Associate Professor The thesis is protected at the Thesis Evaluation Board, held at Nha Trang University at , on This thesis can be found at: The National Library The Library of Nha Trang University SUMMARY OF NEW CONTRIBUTIONS OF THE THESIS Thesis topic: Research on pre-processing and preservation of post-harvested sea grapes (Caulerpa lentillifera J Agardh 1837) Major : Aquatic Product Processing Technology Code: 9540105 PhD student: Le Thi Tuong Course: 2012 Science instructor: Vu Ngoc Boi, Associate Professor Nuyen Huu Đai, Associate Professor Place of education: Nha Trang University Contents: The thesis has gained some new results added to the researches on preprocessing and preservation sea grapes: 1) Proper conditions have been identified for the pre-processing of sea grapes (including the process of washing, recovery of sea grapes) as follows: the suitable conditions for the washing process of sea grapes: amount of water: 15 liters/kg of sea grapes, washing time: minutes and number of times: The suitable conditions for recovery of sea grapes: the rate of sea grapes in water is 2%; growing time is days; the dissolved oxygen in water is mg/l; the light intensity is from 10-15klux, the temperature of medium is 280C Sea grapes planted in these conditions can recover 95.7% with the green intensity of 43.7%, the total aerobic bacteria remain on sea grapes of 323 cfu/g and the sensory qualities of sea grapes meet TCVN 3215-79 2) The thesis has designed and manufactured the circulating planting equipment used in the preliminary processing of sea grapes at pilot scale, the yield of 300kg/batch The equipment works on the principles: the static tank works with the dynamic process and carries out by the circulation of the circulating water and aeration The rectangular equipment is made of the stainless steel 304, size of 6000mm x 1080mm, curved bottom It is equipped with sensors to adjust the temperature in the range of 200C ÷ 300C, the salt concentration from ÷ 10%, the dissolved oxygen concentration from ÷ 20mg/litter Sea grapes pre-processed in days on this equipment have a recovery rate more than 80% and sea grapes meet the quality standards for fresh food according to the current regulations of the Ministry of Health, Vietnam 3) The thesis has identified the suitable conditions for fresh sea grapes preservation procedure by MAP method Fresh sea grapes after pre-processed in the suitables conditions are wrapped in PA packagings, in nitrogen 90% medium, the preservation temperature of from 230C to 290C With the above conditions, fresh sea grapes preserved in 18 days still have good sensory qualities according to TCVN 321579, the rate of damaged sea grapes is about 7%, the weight loss rate is 14.8%, the vitamin content C remains 0.0106 mg/g, the polyphenol content remains 0.077 mgGAE/gFW, DPPH free radical reduction effect is 39.8% compared with that of sea grapes before storage 4) The thesis evaluated the variation in quality of sea grapes after 18 preservation days of MAP method Preservation results shows that after 18 preservation days, the total polyphenol content decreases by nearly 50%, the vitamin C content decreased by 35%, DPPH-free radical reduction decreases by nearly 30%, the protein content decreases by 15% , the lipid content decreases by 18%, the damage rate increases by 6.6%, the weight loss rate increases by 15% The ash and fiber content are quite stable during preservation time 5) The thesis proposes the preliminary processing and preservation of sea grapes by MAP method: collect sea grapes from 35-40 days old, then remove the horizontal stems, collect stems without being damaged, with the same size, green color and length more than 6cm Wash with clean water at a rate of 15 liters/kg, washing time: minutes/times, number of washing: times Then sea grapes are recovered in the continuous circulation equipment with a rate of 2% in the culture medium; the planting time: days; the dissolved oxygen in water: mg/l; the light intensity from 10 to 15klux, the temperature of the culture medium is 280C The recovery period ends, sea grapes are removed, centrifuged to separate 10% of water grasping on the sea grapes After that, pack the sea grapes in PA packagings, pump 90% nitrogen and store them at a suitable temperature of 260C ± 30C After 18 preservation days in the above conditions, the quality of sea grapes is not significantly reduced OPENING Urgency of thesis Sea grape (Caulerpa lentillifera J Agardh 1837) is a species of the genus Caulerpa, which is common in the tropical and subtropical regions Genus Caulerpa is very diverse, Caulerpa lentillifera is the most valuable species In the world, sea grades are known in the 1970s of the 16th century, nowadays they are planted in some countries, especially in Japan, South Korea, India and the Philippines In Vietnam, the sea grapes are known in the early twentieth century Vietnamese scientists have discovered the species of Caulerpa dramatically developing in coastal tidal areas, on densely populated islands, such as Ly Son (Quang Ngai), Phu Quy (Binh Thuan), Phu Quoc (Kien Giang) However, sea grapes discovered in Vietnam have small sizes, they haven’t been planted Sea grapes (Caulerpa lentillifera J Agardh, 1837) was taken from Nhat Ban by Associate Professor Nguyen Huu Dai which are first planted in Khanh Hoa At present, sea grapes are grown in Khanh Hoa, Ninh Thuan, Binh Thuan and Phu Yen provinces The biologic and nutritious values of sea grapes contain many vitamin group A, B, C, polyphenol, chlorophyll and some micro minerals (such as iron, iodine, calcium, etc.) that are necessary for human body Although the protein and lipid content in sea grapes are low, they contain the essential amino acids and fatty acids that human body cannot synthesize itself Especially, sea grapes contain caulerpin which reduces total cholesterol in serum, blood pressure control, anticancer, anticoagulant, antivirus, antioxidant… Consuming sea grapes in Vietnam and in the world is more and more increasing, their price at the Japanese market is about $10/kg of fresh sea grapes Vietnamese sea grapes imported to Japan is about $5/kg of fresh sea grapes Sea grapes in some Asian countries are considered as a high quality vegetable and they are as precious as green salmon caviar Sea grapes contain a lot of water, their water content is up to 94%, their tissue structure is loose and their pigment is easily destroyed by the physical agents Therefore, the fresh sea grapes are quickly spoiled, which reduces their economic values As a consequence, the potential for commercial development of fresh sea grapes products is limited Therefore, the research to propose solutions to prolong the preservation time of fresh sea grapes is necessary The author conducts the thesis: “Research on pre-processing and preservation of post-harvested sea grapes (Caulerpa lentillifera J Agardh 1837)” The purpose of thesis: Build the pre-process and preservation procedure for fresh sea grapes over ten days The objects and scope of research 3.1 The objects of the research Sea grapes (Caulerpa lentillifera) are bought at the farm of Dai Phat B Plus Company, Cam Ranh, Khanh Hoa 3.2 The scope of research 1) Study on pre-process before preservation 2) Study on sea grape preservation by MAP method 3) Study on evaluating the quality by preservation time 4) Propose the pre-process and prservation of sea grapes by MAP method Research methods Using high precisely analytical methods such as atomic absorption spectroscopy - graphite furnace - chemical modifier (CM-GF-AAS) to determine the content of heavy metals Cd, Pb, ; high performance liquid chromatography to determine vitamin A, C, B1 content; gas chromatography to determine the compositions of fatty acids, etc The thesis also uses some Nordic food analysis methods to determine the total number of aerobic bacteria, Escherichia coli and Salmonella Besides, the thesis also used TCVN analyzes to determine the raw protein, the fiber content or the sensory quality At the same time, the thesis also uses mathematical methods in optimizing the experimental process and processing data collection statistics in order to ensure high reliability test results The structure of the thesis The thesis includes 160 pages: 39 pages of overview, 23 pages of research methods, 83 pages of research results, pages of conclusion, 13 pages of references, 39 tables, 83 images, 119 references (51 Vietnamese documents, websites and 65 English documents), 01 page of lists of published works of thesis and 53 pages of annex CHAPTER DOCUMENTAL OVERVIEW 1.1 RESEARCH SITUATION OF SEA GRAPES  Introduction of sea grapes Sea grapes (Caulerpa lentillifera, J Agardh, 1837), which were first described by J Agardh as a species of the Bryopsidale Green algae, Caulerpa, are a common and diverse species living in the tropical and warm temperate regions This species was described by Lamouroux in 1809 with dark green features, cylindrical horizontal stems with many branches, diameter of – 2mm Many vertical stems are grown from horizontal stems Many small branches are grown from vertical stems The end of the branch is spherical bead-like shapes (the grapes) arranged densely on a vertical stem, its diameter of 1.5-3mm This is the valuable part for use, many “unreal roots” on the horizontal stems branch into bunches like fuzz which can cling to mud The characteristics of horizontal stems: they have long horizontal stems, branch into the clam by the root system From horizontal stems, they will grow the vertical stems Figure 1.1 Picture of sea grapes (Caulerpa lentillifera, J Agardh, 1837)  Nutritional values of sea grapes Sea grapes are a kind of seaweed, so they have the typical biological and nutritional values of sea grapes such as low energy, high nutritional and biological values They also have many applications in food processing and pharmaceutical field Sea grapes contain a lot of minerals, fiber, vitamins Especially, they contain almost essential amino acids for the human body, including Asparagine, Glutamate, Serine, Glycine, Histidine, Arginine, Threonine, Alanine, Prolin, Tyrosine, Valine, Methionine, Isoleucine, Leucine, Phenylalanine, Lysine Compared with the genus brown sea grapes, red sea grapes, green sea grapes, sea grapes have higher nutritional values Table 1.1 Compositions of Caulerpa Lentillifera and Ultra Reticulate Compositions Caulerpa lentillifera Ulva reticulate Protein (N=6,25), % 12,49±0,3 21,06±0,42 Fat, % 0,86±0,10 0,75±0,05 Fiber, % 3,17±0,21 4,84±0,33 Ash, % 24,21±1,7 17,58±2,0 Carbohydrate 59,27 55,77 Moisture, % 25,31±1,15 22,52±0,97 Table 1.2 Ash content of sea grapes Ash Unit Content P mg/100 gram dry weight 1030 Ca 780 Mg 630 Zn 2,6 Mn 7,9 Fe 9,3 Cu I g/100 gram dry weight 2200 1424 Table 1.3 Vitamin content (mg/100g) of sea grapes Vitamin Content (mg/100g) Total 170 Vitamin E 2,22 Vitamin C 1,00 Thiamin 0,05 Riboflavin 0,02 Niacin 1,09 Table 1.4 Acid amin content (g/100g dry weight) of sea grapes Fatty acid Content (mg/g dry weight) Threonine 0,79 Valine 0,87 Lysine 0,82 Isoleucine 0,62 Leucine 0,99 Phenylalanine 0,61 Aspartic axit 1,40 Serine 0,76 Glutamic axit 1,78 Glycine 0,85 Arginine 0,87 Histidine 0,08 Alanine 0,85 Tyrosine 0,48 Proline 0,57 Based on the assessment of domestic and international researches related to the processing of sea grapes and based on the preliminary results, the thesis approaches the contents presented in Figure 2.2 Raw sea grapes Quality evaluation Pre-process - Growing time - The rate of sea grapes in the culture medium - Soluble oxygent content - Washing time - Times of washing - The amount of washing water Recovery Separation of water - PA packaging - PP packaging - PVC packaging Packaging Preservation Evaluating the changes in the quality of sea grapes by the preservation time Physical changes Chemical changes Microorganism changes Indentify the preservation method Preliminary processing and preservation of sea grapes Figure 2.2 Schematic approach to the research content of the thesis 2.2.2 Analytical methods: + Determination of moisture: The moisture of the samples is determined by drying method to the constant weight according to TCVN 1867: 2001 + Determination of the protein content: the protein content is determined according to the standard TCVN 4328: 1-2007 + Determination of the lipid content: the lipid content is determined by Folch et al., (1956) + Determination of of the total fiber content: The total fiber content is determined according to TCVN 5714: 2007 + Determination of the ash content: The ash content is determined according to AOAC 923.03-1995 + Determination of the carbonhydrate content: the carbohydrate content is determined according to AOAC: 1990 + Determination of the vitamin C content: the vitamin C content is determined by the iodine titration + Determination of the vitamin B1 content by the fluorescence method based on the principles: When oxidizing vitamin B1 (thiamin) with potassium citrate in alkaline medium will form a green fluorescent thiocromium compound under the ultraviolet light, Thiamin will form a thiocrom molecule To determine the thiamine content, a pure standard solution of thiamin compares with the reference solution Prior to the reaction, thiamin must be released from the sample by enzyme phosphatase, papayolin or takadiatase + Determination of vitamin A contents by the method of high performance liquid chromatography + Determination of fatty acids: Fatty acids are determined by gas chromatography + Determination of Amino Acids: The amino acids are determined by high pressure liquid chromatography + Determination of heavy metal elements: Heavy metals Cd, Pb, are determined by atomic absorption spectrometry (CM-GF-AAS) + Determination of free radical scavenging activity (DPPH): Determination of free radical scavenging activity (DPPH) is determined according to Fu et al (2002) + Determination of total polyphenol content: Determination of total polyphenol content is determined by the method of Fu et al (2011) + Determine the total number of aerobic bacteria according to NMKL86: 2006 + Determination of Escherichia coli by NMKL 96: 2003 + Determination of Salmonella spp according to NMKL 71: 1999 + Determination of the color of sea grapes by analyzing them through the image processing software - Image J The color of sea grapes is captured by the digital camera Nikon coolpix s3300, 16 Megapixel, Nikon STYLE Series (S), Japan The samples of sea grapes are photographed in a black box to prevent the interference from the outside light because the light can make the number wrong The shooting distance is kept fixed for all samples Images in JPEG format are analyzed for red (R), green (G), blue (B) by Image J software, distributed by Natl, Inst Of Healt Bethesda, Md, USA + Evaluation of the sensory quality of sea grapes by the grading method according to the standard TCVN 3215-79 + Determination of the weight loss rate and the damage rate of sea grapes by weighing method with the accuracy of 10-4g 2.3 DATA PROCESSING METHODS Using SPSS 18.0 software for analyzing ANOVA in order to determine statistically significant differences among mean values with  = 0.05% and Post Hoc Test after ANOVA to understand the statistically specific differences among pairs of mean value; Using Design Expert 8.0 software to provide regression equations, mathematical models and relating charts; Using Excel 2013 software to calculate mean values, standard deviation and to draw graph CHAPTER RESULTS AND DISCUSSIONS 3.1 DETERMINATION OF THE QUALITY OF RAW SEA GRAPES After being harvested, sea grapes are transported to the laboratory for removing the vertical stems, damaged sea grapes and unqualified ones, then they are washed, analyzed the chemical compositions, microbiological criteria and some heavy metals The study results show that the ash content accounts for 25.32%, the raw protein content accounts for 12.07%, the raw lipid content accounts for 2.72%, the fiber content accounts for 3.47%, the carbohydrate content (including the fiber) accounts for 59.89%, the vitamin C content accounts for 0.21mg/g, the total polyphenol content accounts for 2.28mg GAE/g and some substances with antioxidant activity (DPPH) account for 47.83% Besides, there is no presence of E.coli and Salmonella in the raw sea grapes These two types of bacteria cause the intestinal diseases that have been prescribed for raw vegetables by the Ministry of Health Cadmium and Pb content of sea grapes are below the level permitted by Ministry of Health according to QCVN regulation 8-2: 2011/BYT 3.2 STUDY ON PRE-PROCESSING RAW SEA GRAPES 3.2.1 The process of washing raw materials The purpose of washing is to remove most microorganisms and some impurities on the surface of the sea grapes, and to minimize the risk of damage The research shows that the appropriate amount of water to wash is 15 liters/kg sea grapes; washing time: minutes/ times and number of washing times: times With these good washing conditions, the microbiological criteria and the quality meet standards 3.2.2 The stage for re-planting raw materials When being harvested, the vertical stems of sea grapes are cut from the horizontal roots The re-planting period helps sea grapes heal the cuts, grow roots and live normally, increase the resistance of sea grapes, prolong the preservation time The study shows that the suitable conditions for re-planting sea grapes are the rate of sea grapes in the culture medium: 2%; the culture time: days; the dissolved oxygen in water: mg/l; the light intensity from 10-15klux, the temperature of culture medium is 280C The sea grapes grown in the above conditions can heal with the rate of 95.7%, green intensity is 43.7%, the total aerobic bacteria remains on the sea grapes is 323 cfu/g and the sensory quality of fresh sea grapes is good 3.2.3 Centrifuging to separate water on the surface of sea grapes At the end of the re-planting stage, the water content on the sea grapes is quite high If they are immediately packaged and stored, they will be quickly spoiled Therefore, centrifuging is necessary The research results show that the percentage of water removed from the surface of fresh sea grapes corresponding to a centrifuge speed 300 rpm in 30 seconds is 10% After being extracted water, sea grapes have enough conditions for preservation 3.2.4 Design of quipments used for the preliminary processing before preservation at the pilot scale, the yield of 100 kg of material / batch The thesis studies the design, produces the circulatory equipment for preliminary processing, the recovery growing of sea grapes is at the pilot scale, the yield is 100kg of material/batch The equipment works on the principles: the static tank working with the dynamic process carried out by the circulation of circulating water and aeration The rectangular equipment is made of the stainless steel of 304, size of 6000mm x 1080mm, the curved bottom The equipment has full range of sensors which can adjust the temperature in the range of +20 ÷ + 300C, the salt concentration in the range of - 10%, the concentration of dissolved oxygen in the range 0-20mg/litter Sea grapes planted within days in this equipment has the recovery rate of more than 80%, even they can recover completely and meet the quality standards of fresh food according to the current regulations of Vietnam Parts for seawater cooling Parts for handling seagrapes Overcover parts Tank Pneumatic Tank Tank Water supply Figure 3.1 The principles of preliminary processing system Notes: MN:air compressor DN: Outdoor unit air RV: Bottom exhaust valve conditioner cooling (Gree) F2: water filter Drying filter P: Pump HS: Heat resistance DL: The hose device with BTL: Throttle the horizontal cover * The operation principles of the system: - The cooling system will cool, control and mantain the temperature of sea water at a temperature of 280C ± 20C At the cooler, the vertical twist hose is insulated with PU (poly urethane) At this device, a heat resistance is installed in case the environmental temperature is below 28°C, the cooler system will stop and the resistance is supplied the electricity to produce heat and make sea water hot before entering the tank for pre-processing - Sea water after being cleaned is pumped through the cooling system to maintain the proper temperature for the pre-processing of sea grapes (28  2)°C, and then it is pumped into the pre-processing tank In the preliminary tank, the aeration system will provide the gas in order to dissolve the oxygen in water and helps sea grapes, water circulate from the bottom to the top As a result, sea grapes at the bottom will be moved upward and expose to light to increase the photosynthesis, they can recover their "health" This process makes the dirt on the sea grapes be removed, which helps sea grapes clean When the dirt is removed from the sea grapes, water will be dirty, then the user will turn on the water recirculation pump system to pump dirty sea water out of the tank, and refill the filtered water back to the tank Thus, sea water in the tank is always circulated in the tank and it is sometimes pumped out of the tank when it is dirty Thus, during operation, the temperature of the sea water in the tank, the dissolved oxygen content, the salt concentration of water in the tank and the illumination intensity of the lighting system are controlled to ensure the proper conditions for photosynthesis, growth and recovery of sea grapes Figure 3.2 The equipment fot recovery of sea grapes, the yield of 300kg material/batch Figure 3.3 Sea grapes are damaged after harvest Figure 3.4 Sea grapes have a recovery after being pre-processed Figure 3.5 The color of the sea grapes before preliminary processing Figure 3.6 The color of the sea grapes after preliminary processing 3.3 SEA GRAPES PRESERVATION AFTER PRE-PROCESSING 3.3.1 Determining the respiratory intensity of sea grapes For MAP method, choosing the suitable packagings for packaging the fresh sea grapes is a successful factor because the semi-permeable membrane of the packaging is directly related to the respiratory intensity of fresh plants For plants with low respiratory intensity, the packageings with low permeability should be chosen and vice versa (acording to Lisa Kitinoja et al, 2004) Therefore, measurement of the respiratory intensity of the sea grapes is the basis for selecting the appropriate packagings in order to prolong the preservation time The study shows that sea grapes have low respiratory intensity The mg of CO2 producing per kilogram of sea grapes in an hour maximizes only 0.008 on the 6th day (0.008 mgCO2/kg.h) Therefore, to prolong the preservation time of sea grapes, they should be wrapped in low permeability packagings (Lisa Kitinoja et al., 2004) PP, PA, PVC packagings are low permeability packagings commonly used in food packaging 3.3.2 Determining type of packagings to pack sea grapes The study of the thesis shows that PA packaging is more suitable than PP and PVC packagings for preserving sea grapes If sea grapes are packed in PA packaging, the sensory quality, chemical compositions and microbial criteria of sea grapes are less variable than those of PP and PVC 3.3.3 Determining the atmosphere environment for preserving fresh sea grapes This research shows that sea grapes are preserved in nitrogen 90% medium, the preservation time is up to 18 days and their sensory quality is good, their weight loss rate is 13.12%, and the damage rate is 6.1 % While sea grapes are preserved in vacuum packaging 65%, the preservation time is only 12 days but their sensory quality is average If there is not the atmosphere modification, the sensory quality is poor after 12 preservation days 3.3.4 Determining the suitable temperature for preserving fresh sea grapes The study shows that the appropriate temperature range for preserving fresh sea grapes is between 230C and 290C When thery are preserved in this temperature range, the preservation time lasts up to 18 days, their sensory quality is quite good The chemical, physical and microbiological norms have slightly variations in comparison with other study temperatures (200C, 320C) 3.4 ASSESSMENT OF PHYSICAL, CHEMICAL AND MICROBIOLOGICAL CHANGES BY PRESERVATION TIME AT THE APPROPRIATE TEMPERATURE (260C ± 30C) Thesis has studied the changes of sea grapes qualily after 18 preservation days by MAP method The results show that after 18 preservation days, the total polyphenol content decreases nearly 50%, vitamin C content decreases nearly 35%, the effect of removing on DPPH radical decreases nearly 30%, the protein content decreases 15%, the lipid content decreases 18%, the spoilage rate increases 6.6%, the weight loss rate increases 15%, the ash and the fiber are stable during the preservation time, 3.5 PROPOSING PRE-PROCESSING AND PRESERVATION PROCEDURES BY MAP METHOD From the study result of this thesis, pre-processing and preservation procedures by map method can be summarized in figure 3.7 Raw sea grapes Selecting and sorting - Amount of washing water: 15lit /kg - Washing time: minutes - Washing times: times Washing Re-planting Selecting and sorting - Sea grapes rate in the culture 2% - Planting time: days - Dissolved oxygen: 8mg/l - Light intensity: 1015klux - Culture temperature: 28oC Centrifuging to dewater: 10% * PA packaging Nitrogen 90% Preservation temperature 260C±30C Sea grapes are preserved in 18 days Figure 3.7 The process of pre-processing and preservation of the fresh sea grapes by MAP method Explain the process: + Raw sea grapes (Caulerpa lentillifera) are planted in Cam Phuc Nam, Cam ranh, Khanh Hoa They are harvested in the period of from 35 to 40 days old Sea grapes after being bought, they are washed with clean sea water and transported to the laboratory for research process + Handling: At the laboratory, sea grapes are removed the horizontal stems The vertical stems with the length more than 6cm, green sea grapes, dark green stems are collected Besides, sea grapes and ramuli with the same size which are not damaged are also collected + Washing: washing sea grapes to remove most microorganisms and impurities on their surface The sea grapes are washed with clean sea water with the amount 15 liters/kg, wahing time: minutes/3 times + Re-planting: The vertical stems of sea grapes are recovered in a continuous circulation equipment with the rate of sea grapes in the culture medium: 2%; growing time: days; the dissolved oxygen in water: mg/l; the light intensity from 10 to 15klux, the temperature of the culture medium is 280C + Finished sea grapes: After finishing the recover process, the unsatisfactory sea grapes are collected and removed for preservation and commerce + Centrifuging to separate water: Finished sea grapes are then centrifuged to separate the water on the surface by manual centrifuge at 300 rpm in 30 seconds The amount of water removed from the surface of sea grapes is about 10% of the total sea grapes weight • Packaging and preservation: After centrifugation, sea grapes are packed in PA packaging, 90% of nitrogen is injected and stored at a suitable temperature of 260C ± 30C Under this condition, the sea grapes will be preserved in 18 days After 18 preservation days, the sea grapes quality is still good, the damage rate is 13.3% and the weight loss is 5.15%, the vitamin C content is 0.0106 mg/gfw, the remaining polyphenol content is 0.077mgGAE/gfw and DPPH free radical reduction activity is 37.6% 3.6 COMPARING THE PRESERVATION TIME AND THE QUALITY OF SEA GRAPES BY BETWEEN MAP METHOD AND THE COMMON PRESERVATION METHOD (TT) The study of the thesis shows that if sea grapes are preserved by MAP method, the preservation time is up to 18 days (3 times higher than the common preservation method), they can maintain a good sensory quality, and they also contains the important characteristics such as antioxidants 39.8%, the total polyphenol content 0.077 mg GAE/gfw, the Vitamin C content 0.0106 mg/gfw and the total lipid content 2.22% While sea grapes preserved by the common preservation method (method is currently used in the sea grapes producing and trading companies in Khanh Hoa and Phu Yen provinces) have only preservation days, however, all chemical components are lost completely, they exist only the fiber, the protein and the ash content Figure 3.8 sea grapes are preserved in days by the common preservation method Figure 3.9 sea grapes are preserved in 18 days by MAP method CONCLUSION AND RECOMMENDATIIONS CONCLUSIONS From the above research results, the thesis has completed all the given research contents and objectives, these results are as follows: 1) The appropriate conditions for pre-processing sea grapes (including the process of washing and recovery of sea grapes) have been identified as follows: the suitable conditions for the washing process: 15 liters / kg of sea grapes, washing time: minutes/ times and number of washing: times The suitable conditions for recovery: the rate of sea grapes in the culture water is 2%; the planting time is days; dissolved oxygen in water is mg / l; the light intensity is from 10-15clux, the temperature of the culture medium is 280C Sea grapes planted in the above conditions have a healing rate of 95.7% with a green intensity of 43.7%, the total aerobic bacteria remaining on the sea grapes of 323 cfu/g and the good sensory qualities according to TCVN 3215-79 2) The thesis has designed and manufactured a circulating equipment used in the preliminary processing of sea grapes at the pilot scale, the yield of 300kg / batch The equipment works on the principle: the static tank with the dynamic process carried out by the circulation of circulating water and aeration The rectangular equipment made of the stainless steel 304, size 6000mm x1080mm, the curved bottom The equipment equipped with sensors to adjust the temperature in the range of 200C ÷ 300C, the salt concentration from ÷ 10%, the dissolved oxygen concentration from ÷ 20mg / lit Two preliminary processing days on the equipment has a recovery rate (normal healing rate) more than 80% and sea grapes meet quality standards for fresh food according to the current regulations of the Ministry of Health, Vietnam 3) The thesis has identified the appropriate conditions for fresh sea grapes preservation by MAP method: fresh sea grapes after being pre-processed under the appropriate conditions are packaged in PA packagings with nitrogen storage medium 90%, the preservation temperature from 230C to 290C With the above conditions, sea grapes are preserved for 18 days, they still have good sensory qualities according to TCVN 3215-79, the percentage of damaged sea grapes is about 7%, the weight loss rate is 14.8%, the vitamin content C remains 0.0106 mg/g, the remaining polyphenol content is 0.077 mgGAE/gFW, DPPH free radical effect is 39.8% compared with that of sea grapws before storage 4) The thesis has assessed the changes in quality of sea grapes after 18 preservation days by MAP The preservation results show that after 18 preservation days, the total polyphenol content decreases nearly 50%, the vitamin C content decreases 35%, DPPH-free radical decreases 30%, the protein content decreases 15%, the lipid content decreases 18%, the damage rate increased by 6.6%, the weight loss rate increased by 15% The ash content and the fiber content are quite stable during preservation 5) The thesis proposes the preliminary processing, preserving sea grapes by MAP method: sea grapes from 35 - 40 days old are collected, then the horizontal stems are removed, strong vertical stems with same sizes, green color, length of more than 6cm are collected After that they are washed in clean water at a rate of 15 liters/kg of sea grapes, washing time: minutes/times, number of washing: times Then sea grapes are recovered in a continuous circulation equipment with a rate of sea grapes 2% in the culture medium; growing time: days; the dissolved oxygen in water: mg/l; the light intensity from 10-15klux, the temperature of the culture medium is 280C The replanting period ends, sea grapes are got out, centrifuged to separate 10% of water grasping on the sea grapes Finally, sea grapes are wrapped in PA packagings with 90% nitrogen and store them at a suitable temperature of 260C ± 30C After 18 preservation days in the above conditions, the quality of sea grapes is not significantly reduced RECOMMENDATIONS Basing on the conducted researches, the thesis proposes to study the improvement of preliminary processing technology, preserving sea grapes and technology transfer to the sea grapes production and trading companies so that these companies can provide consumers with safe and good quality sea grapes LISTS OF PUBLISHED WORKS OF THESIS Le Thi Tuong, Nguyen Thi My Trang, Vu Ngoc Boi, Nguyen Huu Đại, Effect of packaging to quality and shelf-life of fresh sea grapes (Caulerpa lentillifera J.Agardh) Journal of Fisheries science and Technolygy No 3-2016 Le Thi Tuong, Nguyen Thi My Trang, “Research on optimizing pre-treatment of sea grapes (Caulerpa lentillifera J.Agardh)” Science Journal of Can Tho University No 47b (2016), Volume 47b (2016) Le Thi Tuong, Nguyen Thi My Trang, Vu Ngoc Boi, Nguyen Huu Đại, “Optimizing the preliminary processing of sea grapes (Caulerpa lentillifera J.Agardh) after harvesting The summary record of the 6th Natural Sciences and Technology Conference, Khanh Hoa University, 2016 Le Thi Tuong, Nguyen Thi My Trang, Vu Ngoc Boi, Nguyen Huu Đại, Effect of packaging to quality and shelf-life of fresh sea grapes (Caulerpa lentillifera J.Agardh) Journal of Fisheries science and Technolygy No 3-2016 Le Thi Tuong, Vu Ngoc Boi, “Effects of preservation temperature on chemical compositions and preservation time of fresh sea grapes (Caulerpa lentillifera J Agardh) The summary record of the 7th science conference, Khanh Hoa University, 2017 Le Thi Tuong, Vu Ngoc Boi, Nguyen Thi Thanh Thuy,“Effect of the packaging and the preservation temperature to quality and shelf – life of fresh sea grapes (Caulerpa lentillifera J.Agardh, 1837) VBFoodNet 2017 International Conference about Safety and quality in the food chain, from 12th to 14th November 2017 at Nong Lam University-Ho Chi Minh ... (Caulerpa lentillifera J Agardh 1837) The purpose of thesis: Build the pre-process and preservation procedure for fresh sea grapes over ten days The objects and scope of research 3.1 The objects... SITUATION OF SEA GRAPES  Introduction of sea grapes Sea grapes (Caulerpa lentillifera, J Agardh, 1837), which were first described by J Agardh as a species of the Bryopsidale Green algae, Caulerpa,... Ngai), Phu Quy (Binh Thuan), Phu Quoc (Kien Giang) However, sea grapes discovered in Vietnam have small sizes, they haven’t been planted Sea grapes (Caulerpa lentillifera J Agardh, 1837) was taken